i bet this phrase is ALWAYS in the minds of all those humans, sub humans species, humanoids aliens, etc....whose females are either all extinct or the male populations surpass their females or the very few alive females of their species most are sterile and because of this look for others humanoid females for breeding elsewhere.

there are some several science fiction novels and vampires novels that use this kind of examples species tragedy. however, this kind of species mini apocalypse situation are even more common in erotica or erotic novels, whether the sub human species or humanoid alien species mate for life in the typical monogamy way(one male x one female) or in a polygamist but fidelity way(one female married to 2 to 4 or more males for life).

i will post first examples of ordinary scifi fiction and the the erotica ones (dont worry, i wont post sexual stuff in this topic!!!) to show you what kind of explanations their authors give in those novels for such kind of situations.

one of the first novels that came up with this idea in order to create an interesting scifi story is Alan E. Nourse's Raiders from the Rings.

i believe this novel was wrote by an author that seems to had knowledge in biology and genetics, because he give a detailed explanation of the problem that the Spacers human have with their lack of females population:

“Then what do you mean that you have no sisters?” Tom said.
“I mean just exactly that.”
“But why not?”
“Because all the children born to Spacers are male,” Ben Trefon said. “In all our history, no Spacer
has ever fathered a female child. Boys, yes. Girls, never.”

“But that doesn’t make sense!” Joyce protested. “No people could
ever survive with-out—” She broke off in mid-sentence, her eyes widening.

“You’re so right,” Ben said. “Without women, we would grow old, and die, and that would be the end
of us. And that is the reason why we kidnap women on every raid. There’s no other way for us to
survive in space.”

“I just don’t understand,” she said.
“How could you possibly have boys but not girls?”
“Because of the gene changes in Spacer men,” Ben said. “That part is true, you see. There are changes caused by cos-mic radiation. The first men in space were damaged, but there were no mutants.
The damage was invisible and silent: a tiny change in the cells that reproduce life, actually in just one
chromosome pair in those cells, but it was a consistent change that happened every time to every man
who came into space. Oh, there were a few other changes. I’m only eighteen, and I’m already graying
fast; I’ll be white-haired before I’m twenty. And we seem to live a little longer than the average Earthman—our scientists say that our body cells don’t age quite as fast, which helps make up for the high
death rate from accidents in space. But these are minor things. The change in the sex-de-termining
chromosomes is something else altogether.”
“You mean the X-Y pair?”
Ben Trefon nodded. “In Earthmen, women carry a com-plete pair of chromosomes to determine the
sex of the child, while men carry an incomplete pair. One of their X chromo-somes is already
incomplete—the Y chromosome. When a child is conceived, a combination of an X with an X becomes
a female child, while an X and a Y results in a male child.”

“Well, anybody knows that,” Joyce Barron exclaimed. “That’s simple high-school genetics.”
“But it’s also Earth genetics,” Ben said. “In space the single X chromosome that men carry is
damaged. Our scientists still don’t know how, exactly; some of the genes in the X chromo-some are just
put out of commission, so that the X behaves like a Y. And as long as Spacer men can provide only Y
chromosomes, they can never father girls, only boys.”

Presently the girl said, “If what you are saying is true, you had to kidnap women from Earth. It wasn’t a
matter of choice, but sheer necessity.”
“That’s right,” Ben Trefon said. “We have always held to a rigid quota—only enough women to marry
Spacer men as they reached maturity.”

there is one B scifi movie with a similar story but with martian humans spacers or colonist called:

Mars Needs Women: American International Pictures made for TV science fiction film filmed in 1966 which features Tommy Kirk, Yvonne Craig, and Byron Lord.

the explanation of their females problem is this one:

a genetic problem, Martians are producing virtually only male offspring and thus need to import women for the survival of the species. The Martians' non-hostile mission is to bring back to Mars five fertile and single human women.

in this B movie the explanation is that they have a genetic problem in their physiology rather than radiation contamination problems.

another B movie also use this lacked females problem for their stories but instead of the "genetic problem" excuse, they use something else as excuse:

the planet he comes from was destroyed and that he and the other males were able to escape. However, the females of their planet were unable to escape and were killed in the disaster. He then explains that the reason they are taking over the bodies of the Earth men so that they can mate with the women.

Marge Bradley Farrell: Your race has no women, it can't have children. It will die out.
Bill Farrell: Eventually we'll have children with you.
Marge Bradley Farrell: What kind of children?
Bill Farrell: Our kind.

there are several romantic erotic novels that use this kind of explanation to their females problem. other novels of this same genre prefer to use the excuse that their kind have the genetic problem of not being able to father females children or that a disease came to their planet and that killed many of their females and the few of them that are still alive are mostly sterile(only like 1&#37; or less of their remaining females are fertile), so these very human like alien males(sometimes, the authors use sub human species from space colonies instead of the common human like aliens ones)have no others choices but to either kidnap human women and girls or evade our planet for the same matter, always for justified reasons since their survival depend so much on it.

the most popular and best seller erotic romance novel that use this example of lacking female problem is the Dark Series, a group of books by Christine Feehan (once again, genetic problems in their kind that latter books seems to give a impression that this problem is being cause by the contamination that humans are putting on our earth and soils. and this species use the earth soil to sleep and cure themselves from injuries):

Carpathians are on the edge of extinction. There have been few children born to them in the past few centuries; those that have been born are all male and often die in the first year. It has been more than 500 years since a female has been born. Without females, the males are left with a stark choice, "greet the dawn" (i.e. commit suicide) or become vampires, the undead, the monsters of human legend.

there is one erotic romance novel called The Men of Anderas: Jardan By Cheryl Johnson, were human like alien men with this same problem (For more than 2,000 years they have been unable to produce female children because of some plague/disease, so now they must travel to other planets for their brides) also goes to earth in order to find human women to breed with but before they go to this earthe females safari, their leaders put a list of rules that have to being follow so not to cause harm or scicological trauma to the human women and their families and love ones:

In this, our one hundredth year of plague, in an effort to save what is left of our planet, we, the members of the Tribunal of Anderas; hereby declare the following articles to be law:

Technology from alien planets is to be immediately dismantled and destroyed.

No deliberate harm may be brought against any female.

Travel Craft will only obtain females from the worlds chronicled in the Archives of the Ancients.

No female may be taken who has family or close friends who will grieve for her absence.

A male may not choose a mate until this thirty-fifth year.

No male may bond with more than one female in his lifetime.

In order to preserve our bloodlines, no child may be created with a female from any planet other than those listed in the Archives of the Ancients.

Advanced technology will only be used to preserve life and to procure females.

To avoid possible detection, each kingdom of Anderas will be assigned specific areas on the planets of our ancestors in which to locate acceptable females.

No alien being shall be allowed on the planet of Anderas.

Aliens wishing to remain in service to the Anderan Space Exploration Program may apply for permanent residence aboard the orbital space station.

Violation of any article listed above will mean swift and certain death. We take these drastic measures in an attempt to save our dying planet. May the wisdom of the Ancients guide and protect us.

in all this kind of novels(both erotic and non erotic ones)i also notes that the males aliens and sub colonist human species, once they get their hands on a human woman or girl and marry/mate/attach/contract with them, they gave her a better treatment, love and respect that women DON'T get from their human males husbands or boyfriends on earth.

here are some examples in fiction....

from Alan E. Nourse's Raiders from the Rings:

Ben spread his hands helplessly. “What’s she afraid of?” he asked her brother.
“What do you think she’s afraid of? What are we supposed to think you kidnapped her for?”
“To be a mauki, of course,” Ben said.
“What’s a mauki?”
“Why, a mauki’s a… a mauki,” Ben said, staring at the youth. The Earthman sounded as though he
had never heard the word before, and Ben’s confusion deepened. What could he say to explain, if these
people were really ignorant of a mauki’s place in the Spacer world? That a mauki was the wife of a
Spacer? His companion in the dreadful loneliness of a Spacer’s life? The mother of his boys? The proud
and loyal head of the Spacer family? A mauki was all of these things, of course, and far more that was
not so easy to ex-press—at least not now, to two hostile Earth people.

“Then you mean that all of the women who have been kidnapped from Earth have become Spacer
wives?” Tom said.
“Not all of them. No girl has ever been forced to become a mauki, and there are always a few who
refuse to marry, but not very many. For most of them our life has become their life, and they are as loyal
to us as any Spacer man.”

“You never really told us,” she said to Ben. “What is a mauki? We asked you before, but you didn’t
say.”
“It’s so hard to explain,” Ben said. “Mauki isn’t just a word, and a mauki isn’t only a wife and a
mother. My father once told me that he wasn’t sure but he thought the word itself was a corruption of an
old Klickitat Indian word meaning ‘warrior who sings.’ There is something extra special about a
mauki—it has to do with her singing and morale-building. I’m sorry, but this is the best I can do to
answer your question, except that I might say without maukis our life would be empty indeed.”
“Then,” Tom said, “I take it that while all maukis are women, not all women are maukis.”
Ben smiled. “Yes, that’s right.”

“You make us sound beastly,” she said. “But you just ignore
our side of the picture. You don’t pay any attention to how we felt, never knowing when another raid
would come. You don’t understand how our people dreaded those raids, knowing they were coming and
knowing that sisters or daughters would be stolen away and disappear forever. And you don’t say
anything about the mur-der and mayhem your own raiders were responsible for on Earth.”
Ben nodded. “I know people were killed in the raids,” he said. “But it was never murder for the sake
of murder. And that was why we developed the tangle-guns, so we could de-fend ourselves on Earth
raids without hurting people. As for the kidnappings, if Earth had let us come down in peace to find our
wives, there wouldn’t have been any kidnappings, and no kidnapped girl was every forced into marriage
against her will. None of the girls liked the idea at first, but when they heard the songs and stories and
saw the way we lived—” He spread his hands. “You would have to look far and wide to-day to find a
disloyal mauki.”

another examples of this treatment to their new human wives can also be found in this polyandry menage The Kalquor/Earth Saga novels by Tracy St. John and just like the Spacer astronauts men of the novel above called their human wives Mauki, the Kalquor alien men(an alien human like species that poised on the brink of extinction due to the lack of their females also because of disease) call their wives and human wives Matara(mate/child bearer/female child-bearer):

“Do you have any idea what the life of a Matara is like?”
“What does that have to do with anything?”
"The Matara wants for nothing. The rest of the clan would go hungry to feed her. They would go naked to clothe her. They would kill for her; they would die for her. Her smile is their sun; her tears, their hell. She is their goddess to worship and adore.”

Kalquor is a rich planet in ores and natural resources.
Everyone there has a share of the wealth. The Earther Mataras will live in fine homes.
They will enjoy the best foods, clothes, jewels, and any material goods they wish for.
Their clans will care for them, ensuring good health and long lives. You already know
from experience that their medical care is centuries ahead of Earth’s. Most of all, the
clans will love these women unconditionally, for that is the Kalquorian way. Do your
Earth men offer that? Only a few, sadly enough. Most of your men, by your own
admission, see you as slaves to their lusts at the worst and slaves for breeding at best.
Earther women are slaves already! So what if the Earther Mataras fight or beg for their
freedom at first? As time passes, they will know their good fortune and cherish their new
lives. You know your own life will only get better with Rajhir’s clan.”

"You mentioned they were looking for a Matara. What is that?"
"You don’t know? The Matara bears the clan’s children. It's a permanent
arrangement, like Earther marriage, but Kalquorians never divorce. The Matara is the
clan’s beloved, the fourth member of the group when one can be found."

just recently i had also found the oposite side of this kind of sub genre, were the men are the ones either all sterile or totaly extinc. in others words: "Venus need Men" genre.

i manage to found some b movies, some stories in books and even a funny Splicers episode of this topic......

A WOMAN'S WORLD 138-9 Chri Plus by Hilary Jerome:

It's 2142 and Britain, renamed Chriland, is run entirely by women. This a peaceful, tranquil world. There are males, but they are shut away in semenaries for their sperm, while neutered manikins are kept as sexual pets for Chriland's elite women. It is Fra's world, and she is happy in it until Triss, an escaped male, breaks into her home. With her raw sexual instincts aroused Fra finds herself physically and emotionally attracted to this hunky male. But can their love and life among the 'primmies' - a community of dissidents living outside the ordered world of women and run by men - survive? The story's climax, both dramatic and unexpected, makes A WOMAN'S WORLD a stirring fable for our time.

and The Last Man on Planet Earth a 1999 TV movie about a female-dominated society, were the main female character is the ONLY one that realize what is realy WRONG with her present so called "utopia" and star to behave in a more logical and rational matter(UNLIKE the rest of the women there):

Plot

During a war with Afghanistan, an incurable biological weapon called the "Y-bomb", which targets only the male Y-chromosome, is used and results in the eventual deaths of 97% of the world's men. Feeling that they are better off without men, the planet's women decide to outlaw males because they were too violent. 20 years later, scientist Hope Chayse, fearing for the future of the species, conducts a cloning experiment to produce a new male, Adam, genetically enhanced to refrain from violence. When Adam reaches maturity, he soon finds himself on the run from the FBI, and hiding out with small rebel bands of the last surviving men on Earth

Mr. Adam (1946) is the first novel written by Pat Frank with the a funny motto "Mr. Adam Was Wanted By Every Woman in the World":

After a nuclear power plant in Mississippi explodes, it's soon realized that a previously unknown form of radiation is released. The radiation has caused all men on Earth to become sterile, even boys that are still inside the mother's womb. However, ten months after the explosion in Mississippi, a doctor delivers a perfectly healthy baby girl. It's soon discovered that the child's father, who has the surname Adam was miles under the surface of Earth inside an iron mine during the explosion. It would appear that this Mr. Adam is humanity's only hope to stave off extinction.

Sliders TV series scifi also have an episode called LOVE GODS, of this and funny too:

Iraq released a virus in the 1980's which attacked the Y Chromosome (ironically eliminating the male population of Iraq), which went on to kill most of the male population of that world (the survivors had natural immunity to it), so the governments of the world, decided to put all their remaining men in "Breeding centres" to protect them from other governments and to protect them from mobs of women as they are in a race to repopulate, the men are then force to mate with 5-7 women a day, some who escape go to Mexico which has no forced breeding. Australia was the furthest away from the virus to suffer the fewest casulities (starting with 1100 men), so Australia and the US are more antagonistic towards each other.

another novel with irrantional so called "utopia" feminist world were men no longer exist until one is found latter:

World Without Men by Charles Eric Maine and this is the biggest review i found of it: